Critics called Premier Victor Ponta a coward, saying he is using a knee operation to avoid the probe, which has plunged Romania into a political crisis.

Analysts said the surgery was a political calculation that allows the prime minister, a 42-year-old former prosecutor, to buy time after President Klaus Iohannis asked him to resign and he refused. Ponta had earlier survived a vote to lift his immunity, which protects him from some of the corruption charges, and a no-confidence vote.

The premier didn't show up at the anti-corruption prosecutor's office Monday to hear charges of conflict of interest, money laundering and forgery. Instead he sent his lawyer, who explained he was abroad recovering from a knee operation for an injury he sustained playing basketball.

Ponta said Sunday he would ask Iohannis to approve his deputy to take over his duties until he has recovered. The president met Deputy Premier Gabriel Oprea on Monday and later approved his nomination.

Hard-charging Romanian prosecutors have been praised by the U.S. and the European Union for their intensified anti-corruption drive, which is seeking to root out the high-level graft which has pervaded the country's political elite since communism ended in 1989.

Ponta is the most senior figure targeted so far. Prosecutors say he is suspected of forging receipts for work he did as a lawyer from 2007-2008 while he was also a lawmaker and of receiving payments from another lawyer whom he later appointed as minister three times. Ponta denies wrongdoing.

Ponta's brother-in law, his former finance minister and other colleagues are also being probed for corruption. The prosecutor's office secured 1,051 convictions since January 2014, including a former prime minister, a former deputy prime minister, seven former ministers, four lawmakers, one European Parliament lawmaker, 39 mayors, 25 magistrates and two business tycoons.

Political scientist Cristian Parvulescu said Ponta's operation abroad was a "political calculation" and time-buying tactic.

"Victor Ponta won't resign for moral reasons, only for political reasons and they haven't appeared yet," he said in a telephone interview.

"Ponta is weakened politically. He has won a month, but he will be overthrown or will resign," he said. "Lawmakers are preparing an alternative."

Ponta suggested he would not return to Romania for three weeks and justified his absence by saying he hadn't taken a day off since becoming prime minister in April 2012. Three years ago, Ponta weathered accusations of plagiarizing his doctoral thesis and refused to resign then.

"I haven't been away from the job for a single day or stayed in bed. I haven't had a cold since I became premier. I was always working," he told Antena 3 TV station Sunday by telephone, contradicting official records which show he has taken time off. "I think things got on top of me, tiredness and stress."

The leader of the opposition Liberal Party, Alina Gorghiu, called Ponta "a coward who doesn't care about the image of the country," and is seeking "medical asylum outside the EU." Critics say he chose to undergo surgery in Turkey, where Romania's elite sometimes seek medical treatment, because it is less committed to democratic principles than the EU.

Gorghiu's party said it was gathering signatures for a new no-confidence bid.

According to the constitution, the prime minister is allowed to take 45 days off for medical reasons.

Since arriving in Turkey, Ponta has used Facebook to communicate, regularly posting messages. On Monday he wished his mentor and former Prime Minister Adrian Nastase a "happy birthday." Nastase was jailed twice for corruption charges.

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This story had been corrected to fix the spelling of Bucharest in the dateline.